This invention relates to a rotating electric machine having a cooling passage, the rotating electric machine functioning as a motor or a generator.
One type of rotating electric machine is provided with a plurality of stator cores connected with each other in a circular orientation. A cooling passage is provided which is defined by two adjacent stator cores and a circular resin mold which closes the slot openings. In this type of rotating electric machine, there is the possibility of leakage of cooling medium as a result of cooling shrinkage in the resin mold.
Tokkai Hei 5-328656 published by the Japanese Patent Office in 1993 discloses a rotating electric machine provided with a housing member for a bearing of the rotor. The bearing housing member contacts the resin mold and suppresses cooling shrinkage in the resin mold. In this rotating electric machine, a coefficient of linear (thermal) expansion for the bearing housing member is the same as that for the magnetic steel plates comprising the stator core. Consequently, the degree of stress between the stator core and the resin mold is reduced and it is possible to prevent damage to the resin mold as a result of cooling shrinkage.
However since large-scale rotating electric machines are assembled by fitting the bearing housing member after forming the resin molding on the stator core, it is necessary to carefully control the dimensions of the bearing housing member. From the point of view of cost and productivity, this type of structure is not used in the prior art with respect to large-scale rotating electric machines.
It is therefore an object of this invention to avoid the generation of stress between the stator core and the resin mold during cooling shrinkage of resin molding in all rotating electric machines including large-scale rotating electric machines.
In order to achieve above object, this invention provides a rotating electric machine comprising: a rotor; a circular stator having a plurality of stator cores connected about the periphery of the rotor and an annular member disposed on the outer periphery of the plurality of stator cores; a case for housing the rotor and the stator; a cylindrical resin molded section formed along the inner peripheral face of the stator and covering slot openings between stator cores; and a cooling passage extending along an axial direction of the rotor and being defined by adjacent stator cores and the resin molded section.
The annular member is formed from a material which has a larger coefficient of linear expansion than the magnetic material comprising the stator cores.
The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.